The present invention relates to a ferromagnetic material sputtering target for use in the deposition of a magnetic thin film for a magnetic recording medium, and particularly a magnetic recording layer of a hard disk adopting the perpendicular magnetic recording system, and refers to a sputtering target capable of inhibiting the generation of particles during sputtering.
In the field of magnetic recording as represented with hard disk drives, a material based on Co, Fe or Ni, which is a ferromagnetic metal, is being used as the material for a magnetic thin film in a magnetic recording medium. Composite materials of Co—Cr-based or Co—Cr—Pt-based ferromagnetic alloys with Co as its main component and nonmagnetic inorganic materials are being used for the recording layer of hard disks adopting the perpendicular magnetic recording system which was recently put into practical application.
A magnetic thin film for a magnetic recording medium such as a hard disk is often produced by sputtering a ferromagnetic material sputtering target having the foregoing materials as its components in light of its high productivity. A hard disk drive which is used as an external recording device is demanded of increased recording density with each passing year, and the reduction of particles that are generated during sputtering is also strongly demanded pursuant to the increase in recording density.
For example, Patent Documents 1, 2, and 3 describe a sputtering target configured from a magnetic phase of cobalt-based metal and a nonmagnetic phase of metal oxide, wherein the generation of particles and arcing during sputtering is reduced by pulverizing oxide phase grains.
Nevertheless, since chromium oxide is not easily sintered, if chromium oxide is subject to sufficient sintering, there are cases where grains of components other than chromium oxide will grow and, when a target with a coarse structure resulting from the foregoing grain growth is used for sputtering, there is a problem in that the generation of particles will increase. Meanwhile, if sintering is restrained in order to suppress the foregoing grain growth, the target density will deteriorate and there is a similar problem in that the generation of particles will increase.
Patent Document 1: JP-A-2009-215617
Patent Document 2: International Publication No. 2007/080781
Patent Document 3: Japanese Patent No. 4837801